Transterrestrial Musings

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More Throwing Away Of Our Future

I got another interesting email in response to this week's Fox column, this time from Scott Benson, who writes:

I enjoy reading your musings, and always find things to agree and disagree with. But this time, I must be missing your point.
It seems to be: In a high flight rate mission model, reusable launch vehicles make much more sense.

Well, that is interesting, and I tend to agree; but it is totally irrelevant for the next 20 (?) years minimum. The mission model for the foreseeable future is 10's of launches per year, not thousands, as much as we wish it would be the latter. And for better or worse, the NASA mission model is primarily about 5 human space flights per year, carrying 3 - 7 people to the ISS, with an assortment of 10 or so other earth and interplanetary missions. It is perfectly rationale, under that reality, to use expendable launch vehicles and reusable crew modules.

Well, here's where the disagreement lies. There is no such thing as a mission model. This is just a fiction that government bureaucrats come up with to generate requirements for potential new government launch systems. Mission models were always, to me, the absurdity of activities like the Space Transportation Architecture studies (some of which I participated in, and even managed). There is, in fact, no particular need for us to do anything at all in civil space, at least not in civil manned space.

"Mission models" are driven by launch capability--not the other way around. We have a "mission model" to deliver a certain number of crew to space station per year. Why? Not because there's anything in particular for those people to do in space, but because we built a space station of a certain size, and that's how many it holds. Why was it that size? Primarily because we decided from day one that one of its stone-tablet, not to be even questioned, program requirements was to put it up in pieces with the Shuttle.

For the amount of money that we spent on station to date, we could have built a station ten, or even a hundred times the size, had it been important to do so. But the primary purpose of station was to give JSC and Marshall something to do after the Shuttle development was complete, and to justify the development of the Shuttle. So as an artifact of that decision, we end up with a "mission model" that requires delivering a couple dozen people to space for the next twenty years.

Had Reagan said, instead of asking for a scientific space station, that he wanted a habitat for a hundred people in orbit, and he didn't care how NASA did it, he could have had it for the same money (after diverting a few billion to a heavy-lift Shuttle derivative that could launch huge modules, a la Skylab, out of ET barrel sections). If he'd done so, we'd now have a "mission model" of many hundreds of annual crew transfers, rather than a dozen or so.

There's a phrase for basing present decisions on past flawed ones. It's called "throwing good money after bad."

NASA's options are: 1) Use STS forever and cross their fingers 2) Build a reusable launch system (that certainly doesn't seem to be in favor) 3) Buy the commercially available low cost reusable launch services 4) Go with expendables to mitigate STS life risks, and to wait until the commercial reusable launch services arrive.
Are you in the "build it and they will come" camp, with the assumption that building a commercial RLV will instantly lower the price of access to space and result in rapid growth in flight rate? I suppose it could happen, and that your article is trying to convince the entrepreneurs to invest their billions. Maybe that is the point. I'll check your feedback to see if I guessed it right.

I'd go with a combination of options 1 and 4: use STS until the commercial reusable systems come along, but also put into place government policies that encourage (rather than discourage) the latter.

I am in the "build it and they will come" camp, and I do want entrepreneurs to invest (though I don't believe that it will require billions, at least not to get operating revenue and profits). But I'm also in the camp that wants to see a fundamental rethinking of the purposes and means of government space policy. I'd like to make it more transparent, and be explicit about why we even have a manned space program.

The dirty little secret, of course, is that we do it for jobs in Houston and Huntsville and Florida and California, and international prestige, (and more recently as a means of providing foreign aid to Russia without dipping into the State Department's budget), not because we're trying to accomplish anything in particular in space.

If it's to open up space as a frontier, and truly become a space-faring society, the current path is not going to get us there, and developing a new generation of expendable launchers is on that current path. For the limited amount of activity proposed by NASA's "mission model," there's no point in ever developing anything new. It cannot pay for itself.
We're still flying B-52s, and we can probably get decades of life out of the Orbiters as well, given the low flight rate.

If, on the other hand, we make a conscious decision to develop a lot more capability, then there are policy routes to get there. I would propose an airmail-like subsidy, having the government purchase thousands of round-trip tickets at much lower costs than current, using what it needs for its own purposes, and then auctioning the rest back on the market.

And NASA should have absolutely no say in the vehicle design. They need to get out of operations entirely, and get back into a NACA mode (the way they would have operated had we not panicked after Sputnik).

But why bash NASA for looking at reasonable alternatives, especially given the options?

Because I don't think they really have a problem. They just want another development program. It's just the next way to sell X-38.

I also object to your characterization of "converted munitions". The current generation of Atlas and Delta rockets have almost (or absolutely) nothing in common with their missile ancestors. The designs of these vehicles have been driven by one thing over the last 20+ years, making a profit in a commercial market place (a concept I believe you are in favor of). I doubt either LockMart's or Boeing's mission statements read "We are extending the application of first generation ballistic missiles into their 6th decade!!!"

That's a semi-fair criticism. They aren't literally converted munitions. But they are based on the same philosophy that goes all the way back to their ICBM progenitors, and it's not one that will ever give us the reliability and low costs that are absolutely necessary to do truly ambitious things in space, and to open it up to society. As for making a profit delivering comsats, that's nice, but it has very little to do with opening up space to the masses, which is my goal, and one that I believe is achievable given a change in mindset among the policy and investor communities, and the public.

That was the point of my column (and most of my columns).

I also hope the incredible happens, and someone finds the way to open space to all of us. Thanks for your efforts in getting the word out.

And thank you for putting in another quarter. Hope you enjoyed the rant.

Posted by Rand Simberg at October 18, 2002 03:07 PM

Comments

Actually, this is an unrelated question for anyone who may be able to answer it. I'm a student working on a group report on either the destiny lab module or CRV, anc am having great difficulty finding technical design information. How does one go about finding real technical information on NASA projects, specifically the destiny module and CRV? I'm trying the technical reports server (CASI) and spacelink.nasa.gov, but all I'm getting is pretty pictures and crew flight reports when I search these subjects. If anyone has a suggestion, I would be much obliged!

Posted by James at October 18, 2002 04:21 PM

I'd post the question over on Usenet, on sci.space.tech or sci.space.history.

Posted by Rand Simberg at October 18, 2002 04:36 PM

Ah, so I got it half right: convince the entrepreneurs to bring their (arguable) billions, AND convince the White House (perhaps through the public) of the ridiculous state we're in, so that they might step in and dismantle the current NASA/human space flight situation. Your response helped!

A note on mission models. Yes, NASA may not do a particularly good job of developing them, but a commercial entity would do exactly the same thing, except it's be called a market assessment or something. The problem, as you indicate, is that the NASA mission models are bound by the context of the NASA space flight politics. They aren't of much help to the White House in making dramatic policy decisions.

Posted by Scott Benson at October 19, 2002 05:36 AM

Well, actually, rumor has it that the White House (and O'Keefe and Stadd and Pace) are seriously thinking about dismantling the current structure, having floated ideas about spinning off the Shuttle to a separate Space Transportation Authority, thus taking it away from NASA. The same could then be done with space station.

And I didn't say anything about the Administration using mission models to make policy. In fact, I said it should be the other way around.

And there's a difference between a mission model and a market assessment. The latter assumes price-demand elasticity, and is actually based on market research (like the recent Futron report).

Posted by Rand Simberg at October 19, 2002 08:59 AM

I want us in space.

I wish NASA would budget for better PR.

And stop over-deisgning. On this one, a cousin was involved with one of the first commercial sats. Among other things, it was supposed to extend a boom at the end of which were some electronics - but how to deliver the electricity to the components? After listening to better-educated nd more-experienced people argue about metallic-sheathed cables (think public telephones), how much power could be needed for carrying the extra burden of wiring for the motor to extend the boom, etc. my cousin pointed out that since the satellite was to be short-lived no fancy stuff was needed. A fan-folded regular extension cord from the supermarket, with the folds held by an elastic from someone's desk drawer, would do: the elastic would break with minimal pressure (especially at space temperatures), the weight was negligible, and if it eventually shorted out it should still last the length of the mission.

And it did.

Posted by John Anderson at October 20, 2002 10:35 PM

James, re the CRV:

http://www.astronautix.com/craft/hl20.htm

HL-20 lifting body
The "luxury" crew rescue vehicle option was the Langley Research Center's $2-billion HL-20 which was loosely based on a Soviet spaceplane design.
Credit: NASA

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Class: Manned. Type: Rescue. Nation: USA. Agency: NASA. Manufacturer: NASA Johnson.
Also known as ACRV (Assured Crew Return Vehicle), CERV (Crew Emergency Return Vehicle) and PLS (Personnel Launch System). NASA Langley design for a manned spaceplane as a backup to the space shuttle (in case it was abandoned or grounded) and as a CERV from the Freedom space station. Lifting body re-entry vehicle based on the Russian BOR-4 design. Designed for two flight crew, eight passengers, piloted landing at airfield on landing gear. During launch a fairing from the Titan IV booster to the spacecraft would have had solid rocket motors (154,000 kgf) for launch abort, with parachutes for a tail-down water landing. Although studied by contractors and a full size mock-up was built, the design was not selected for further development. Soyuz was designated as the International Space Station CERV. When doubts about the availability of Soyuz developed in 1995, NASA proceeded with development of the X-38, a NASA Johnson concept - a smaller version of the X-24 lifting body with a parafoil.

History

In 1983, the Vehicle Analysis Branch began the investigation of the BOR-4 small spaceplane being orbited several times by the Soviets starting in 1982 and recovered in the Indian Ocean and Black Sea. During recovery operations of the space plane in the Indian Ocean, an Australian P-3 Orion aircraft obtained photographs of the vehicle both floating in the water and being hauled aboard the recovery ship. This provided valuable insights into the shape, weight and centre of gravity of the vehicle. Based on this information, small wind tunnels models were produced and tested in the NASA Langley wind tunnels. The results demonstrated the vehicle had good aerodynamic characteristics throughout the speed range from orbital entry interface to low supersonic speeds. Wind tunnel tests showed configuration directional stability at all speeds from subsonic to Mach 20, trimmed to maximum L/D with 10 degree elevon deflections in subsonic range, with no control deflection at Mach 0.6 to 0.9, at 3 degree angle of attack in transonic range, and then again with no deflection from Mach 2.0 to Mach 20. The Soviet design had a 2,040 km cross-range capability and an outstandingly benign thermal profile at peak heating conditions.

Langley Research Center (LaRC) continued to investigate the aerodynamic characteristics of this shape and examined some shape changes to improve the low speed aerodynamics from transonic down to subsonic speeds. LaRC personnel who had worked in the 1960's on lifting bodies, especially the HL-10, were available to conduct these aerodynamic and shape modification tests.

Crew Emergency Rescue Vehicle

As a result of the 1986 Space Shuttle Challenger accident, interest rapidly developed in developing a crew emergency rescue vehicle (CERV) for the proposed US/International space station. If the Shuttle was unavailable for use or station astronauts had to return to Earth in an emergency this would provide continued manned assured access to space. In late 1986, Langley began to study the use of the BOR-4 lifting body shape as a CERV. This involved internal layouts, weight estimations, and centre-of-gravity estimates for a vehicle of large enough scale to accommodate up to 8 space station crew members.

This concept, designated the HL-20, was designed for low operations cost, improved flight safety and conventional runway landings. The proposed Personnel Launch System (PLS), would utilise the HL-20 and an expendable launch system to provide manned access complementing the Space Shuttle. A full-size engineering research model of the HL-20 was constructed by the students and faculty of North Carolina State University and North Carolina A & T University for studying crew seating arrangements, habitability, equipment layout and crew ingress and egress. This engineering research model was 8.84 m long and provided the full-scale external and internal definition of the HL-20 for studies at the Langley Research Center.

The PLS mission was to transport people and small amounts of cargo to and from low-Earth orbit. Although not approved for development, the PLS was designed as a complement to the Space Shuttle and was considered for addition to the manned launch capability of the United States for three main reasons:

Assured manned access to space. In that era of Space Station Freedom and subsequent missions of the Space Exploration Initiative, it was felt to be imperative that the United States have an alternate means of getting people and valuable small cargo to low-Earth orbit and back should the Space Shuttle be unavailable.

Enhanced crew safety. Unlike the Space Shuttle, the PLS would not have main propulsion engines or a large payload bay. By removing large payload-carrying requirements from personnel delivery missions, the PLS would be a small, compact vehicle. It is then more feasible to design an abort capability to safely recover the crew during critical phases of the launch and return from orbit.

Affordable costs. As a small vehicle designed with available technologies, the PLS was forecast to have a low development cost. Subsystem simplification and an aircraft approach to PLS ground and flight operations would also greatly lower the costs of operating PLS.

Candidate Shapes
The two designs considered for PLS differed in their aerodynamic characteristics and mission capabilities. The Johnson Space Center's approach used a ballistic bi-conic design shape (L/D of .75 to 1.0) with a parafoil for a precision landing. The Langley Research Center's HL-20 design was a lifting body that could make a conventional runway landing on return from orbit.

History of Lifting-Body Research

Predating and influencing the design of the Space Shuttle, several lifting body craft including M2-F2, M2-F3, HL-10, X-24A, and X-24B were flown by test pilots during the period 1966-1975. The M2-F2 and the HL-10 were proposed in the 1960s to carry 12 people to a space station following launch on a Saturn IB. In the Soviet Union, the BOR-4 shape was developed and studied by Langley based on recovery photographs. The HL-20 PLS concept evolved from the BOR-4 with modifications based on experience with the early US shapes. The "HL" designation stands for horizontal lander, and "20" reflected Langley's long-term involvement with the lifting body concept, which included the Northrop HL-10.

Advantages of Lifting Bodies

A lifting-body spacecraft, such as the HL-20, would have several advantages over other shapes. With higher lift characteristics during flight through the atmosphere while returning from orbit, the spacecraft can reach more land area, and the number of available landing opportunities to specific sites would be increased. Loads during entry, in terms of g-forces, would be limited to about 1.5 G?s. This was important when returning sick, injured, or deconditioned Space Station crew members to Earth. Wheeled runway landings would be possible, permitting simple, precision recovery at many sites around the world, including the Kennedy Space Center launch site.

HL-20 PLS Missions

Delivery of passengers to Space Station Freedom would be the primary mission of a PLS. For the baseline space station mission, the crew size would be eight passengers (a space station crew) and two flight crew members.

A typical PLS mission operation scenario, using an HL-20, would commence at the Kennedy Space Center with the HL-20 being processed horizontally in a vehicle processing facility while an expendable launch vehicle is processed vertically in a separate facility. The launch vehicle and HL-20 would be mated at the launch pad and the launch sequence initiated as the space station passes over the launch site.

Following launch, the HL-20 would initially enter a low 185 km orbit to chase after the space station and then transfer up to the space station orbit altitude of 410 km. After rendezvous and docking at Space Station Freedom, crews would be exchanged, followed by a HL-20 return to Earth at the earliest opportunity.

The HL-20 would land horizontally on a runway in manner similar to the Space Shuttle. Total mission duration would not exceed 72 hours.

Other potential missions defined for a PLS included the orbital rescue of stranded astronauts, priority delivery and observation missions, and missions to perform satellite servicing. For these other missions, the basic HL-20 design would be unchanged, but interior subsystems and arrangements would be modified according to crew accommodations, duration, and equipment required for the particular mission.

HL-20 PLS Launch Vehicles

The HL-20 concept of the PLS was adaptable to several launch vehicle concepts. Titan III was an existing booster system which could be used for unmanned prototype launches but would require modification to be used as a manned system. A future launch system option at that time was the National Launch System under study by the Air Force and NASA. Choice of a launch system for the HL-20 PLS would depend both on the required date of initial PLS operations and the cost of booster development and launches.

Design Features

The design philosophy of the HL-20 PLS concept was to complement the Space Shuttle with safe, reliable manned transportation at the lowest cost. Of utmost importance was crew safety with emphasis being given in the HL-20 design to launch abort situations and the protection of the crew during vehicle recovery. Other requirements focused on minimising life-cycle costs of the system by insuring simple operations, low-cost manufacturing, and high utilisation potential.

With an overall length of 8.84 m and span across the wing tips of 7.16 m, the HL-20 PLS concept would be a much smaller craft than the Space Shuttle Orbiter. In fact, the HL-20 could fit within the payload bay of the Shuttle with wings folded. Overall, the HL-20 would weigh 10,000 kg without crew compared to the Space Shuttle Orbiter's empty weight of 84,000 kg. The space available inside for the crew and passengers, although less than the Shuttle, would be more than found in today's small corporate business jets.

A very important aspect of the HL-20 PLS concept which would help insure low cost operations was its design for maintainability. Large exterior access panels permitted technicians easy access to subsystems which would be exposed and easily replaced if required. The vehicle would be processed in a horizontal position. Selection and design of subsystems would emphasise simplicity and reduce maintenance requirements. For example, hydraulic systems would be replaced by all-electric controls. Unlike the Space Shuttle, the HL-20 would not have a payload bay or main engine propulsion, thereby reducing the processing time. The thermal protection system would be similar to the Space Shuttle's, but the much smaller size of the HL-20 would result in major reductions in inspection and maintenance times. These design changes and subsystem simplifications, along with the adoption of aircraft maintenance philosophies, could reduce the HL-20 processing man-hours to less than 10 percent of that used for the Space Shuttle Orbiter.

The design of the HL-20 PLS concept had taken into account crew safety and survivability for various abort modes. The interior layout with a ladder and hatch arrangement was designed to permit rapid egress of passengers and crew for emergencies on the launch pad. For on-the-pad emergencies or during launch where time is a critical element (launch vehicle fire or explosion), the HL-20 would be equipped with emergency escape rockets that would rapidly thrust the PLS away from the booster. The method was similar to that used during the Apollo program. Once at a safe distance, a cluster of three emergency parachutes would open to lower the vehicle to a safe ocean landing. Inflatable flotation devices ensured that it rode high in the water, with at least one of two hatches available for crew emergency egress.

HL-20 Lifting-Body Research

A significant amount of research effort went into experimental and computational investigations of the baseline HL-20 shape. The goal was to amass a data base of information about the system to aid in management decisions for PLS development.

Using the extensive wind tunnel resources at Langley, researchers compiled a comprehensive aerodynamic and aerothermodynamic data base on the HL-20 concept spanning the entire speed range the PLS would fly through. Several models were built for testing in the various tunnels ranging from a 1.5 m model used for force and moment tests at low speeds to 15 cm models used in hypersonic tests. Results showed the shape possesses good flying qualities in all flight regimes. In addition to measurements of aerodynamic properties, experimental aerothermodynamic heating studies were performed. A new thermographic phosphor technique was used to study the heat transfer characteristics of a HL-20 model in high-speed wind tunnel tests. The model, coated with a phosphor, radiated at varying colour intensities as a function of temperature during test when illuminated by ultra-violet light.

Computational fluid dynamics (CFD) codes, which mathematically simulate the flow field in the vicinity of the HL-20, were also used at Langley. These advanced computational grid techniques were used in conjunction with wind tunnel tests to study patterns of flow field phenomena, shock waves, stability and control and heating on the windward and leeward surfaces of the vehicle. Such computational analyses become critical in regimes where wind tunnels cannot duplicate the entry environment. For example, heating in the flight environment on this concept was predicted to be within the limits of Space Shuttle-based high-temperature, reusable surface insulation (HRSI) everywhere except at the nose of the vehicle, where Shuttle-based carbon-carbon thermal protection was required.

Two of the major questions that had to be answered about the lifting-body concept were how to control the HL-20 during the high-heating portion of the re-entry from orbit, and what was the proper guidance scheme for use in the landing phase to enhance its flying qualities. Langley researchers used a six-degree-of-freedom trajectory analysis technique along with mass, inertia and aerodynamic properties of the vehicle to investigate the entry phase of flight.

Results showed that the concept could be controlled through the hypersonic entry using only 14 kg of reaction control thruster fuel in nominal cases, or less than 90 kg of fuel in cases where the vehicle centre of gravity was offset and the upper atmosphere density and wind profiles were off-nominal. The entry analysis also showed the effects of using the vehicle's aerodynamic surfaces in conjunction with thrusters for control purposes.

In addition to computer modelling of vehicle controllability during entry, a flight simulator was set up at Langley to permit pilots to study the final landing phase of flight. Starting at an altitude of 4,600 m, the simulation presented the pilot with a realistic view of the approach to a runway landing. Using a side-stick controller, pilots, including one who had flown the X-15 rocketplane and the lifting bodies, demonstrated this configuration to be controllable and capable of pinpoint landings.

In October 1989, Rockwell International (Space Systems Division) began a year-long contracted effort managed by Langley Research Center to perform an in-depth study of PLS design and operations with the HL-20 concept as a baseline for the study. Using a concurrent engineering approach, Rockwell factored supportable, efficient design and operations measures into a detailed, cost-effective design along with a manufacturing plan and operations assessment. A key finding of this study was the realisation that while design and technological factors can reduce costs of a new manned space transportation system, further significant savings are possible only if a new operations philosophy is adopted -- treating PLS in a manner similar to an operational airliner rather than a research and development space vehicle.

In October 1991, the Lockheed Advanced Development Company began a study to determine the feasibility of developing a prototype and operational system. The study objectives were to assess technical attributes, to determine flight qualification requirements, and to develop cost and schedule estimates.

A co-operative agreement between NASA, North Carolina State University and North Carolina A&T University led to the construction of a full-scale model of the HL-20 PLS for further human factors research on the concept. Students at the universities, with requirements furnished by Langley and guidance from university instructors, designed the research model during their spring 1990 semester with construction following during the summer.

The human factors research objectives, using this model, were to assess crew ingress and egress operations, assess crew volume and habitability arrangements, and determine visibility requirements for the crew during critical docking and landing operations.

The testing, using Langley Research Center volunteers as subjects, was completed on the HL-20 model in December 1991. Langley volunteers, wearing non-pressurised flight suits and helmets, were put through a series of tests with the craft placed in both horizontal and vertical modes.

The horizontal study found, for example, that a 10-member crew had adequate volume to quickly and in an orderly manner get in and out of the spacecraft. The available volume and proximity to others was found to be more than reasonably acceptable for a 10-member crew. Recommendations for revision included: more side-head room for the last row of seats to accommodate those taller than 170 cm; a wider aisle; removable seats and more training could improve emergency personnel capabilities and performance; more downward viewing capability for the pilot; structural supports in the windows could reduce viewing; and the cockpit display and seat design must be integrated with window placement.

Testing the HL-20 in a vertical position as oriented for launch posed a new set of factors. Getting in and out of the spacecraft, for example, required climbing through a hatch and up or down a ladder. In the horizontal mode, crew members walked along an aisle leading through the tail, which would be the exit-entry path at a space station or on the ground after a runway landing.

Partial-pressure suits, borrowed from the Johnson Space Center in Houston, were used for part of the study. Participants noticed less head room and restricted movement with the bulkier and heavier suits.

The results of the human factors studies showed where improvements in the baseline HL-20 design were desirable. These improvements would have little impact on overall vehicle shape or aerodynamic performance.

In the end, space station Freedom became the International Space Station. As the initial crew emergency rescue vehicle, the Russian Soyuz spacecraft was selected. However NASA, looking for a higher-capacity alternative and concerned about reliable availability of the Soyuz in the future, did begin development of the X-38 CERV in 1997. The X-38 was however based on the Johnson concept of parachute-assisted landing, and used the pure-USA X-24 lifting body shape....

Craft.Crew Size: 10. Design Life: 3 days. Orbital Storage: 3.00 days. Total Length: 8.9 m. Maximum Diameter: 7.2 m. Total Habitable Volume: 16.40 m3. Total Mass: 10,884 kg. Total Payload: 545 kg. Electrical System: Batteries.

Module: Reentry Vehicle. Purpose: Manned space plane. Payload: 545 kg. Crew mass: 1,270 kg. L/D Hypersonic: 1.8. Electric system type: Batteries.

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HL-20 Chronology

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01 January 1983 NASA Langley begins studies leading to HL-20
The Vehicle Analysis Branch began investigation of the Soviet BOR-4. Small models were tested in NASA wind tunnels and demonstrated that the vehicle had good aerodynamic characteristics throughout the speed range from orbital entry interface to low supersonic speeds. The Soviet design had a 2,040 km cross-range capability and an outstandingly benign thermal profile at peak heating conditions. Therefore Langley adopted it as a baseline for a Crew Emergency Rescue Vehicle to back-up or replace the shuttle after the 1986 Challenger accident.

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01 October 1989 Rockwell begins year-long contracted study of HL-20
Rockwell International (Space Systems Division) began a year-long contracted effort managed by Langley Research Center to perform an in-depth study of Personnel Logistics System design and operations with the HL-20 concept as a baseline. The spaceplane would supplement the shuttle in support of the Space Station Freedom.

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01 October 1991 Lockheed feasibility studies of HL-20
Lockheed Advanced Development Company began a study to determine the feasibility of developing a prototype and operational system. The study objectives were to assess technical attributes, to determine flight qualification requirements, and to develop cost and schedule estimates.

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01 December 1991 HL-20 Mock-up tests completed
NASA, North Carolina State University and North Carolina A&T University built a full-scale model of the HL-20 for human factors research on the concept. In the end, space station Freedom became the International Space Station. As the initial crew emergency rescue vehicle, the Russian Soyuz spacecraft was selected. However NASA, looking for a higher-capacity alternative and concerned about reliable availability of the Soyuz in the future, did begin development of the X-38 CERV in 1997. The X-38 was however based on the Johnson concept of parachute-assisted landing, and used the pure-USA X-24 lifting body shape....

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Bibliography:

Aviation Week and Space Technology, "HL-20", 1991-07-15, page 52.
NASA Facts On-Line, "HL-20 MODEL FOR PERSONNEL LAUNCH SYSTEM RESEARCH", NF172 - April 1992. Web Address when accessed: http://oea.larc.nasa.gov/PAIS/HL-20.html.

Posted by David Davenport at October 24, 2002 04:28 PM

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